Drive mechanism



States This invention relates to a drive mechanism and most particularly to a ratchet type drive mechanism.

It is a general object of the invention to provide an improved drive mechanism.

It is another object to provide a drive mechanism wherein overpowering return torque applied to the driven components thereof is controllable by the driving forces which are overpowered.

A specific object is to provide a drive mechanism in which overpowering or overriding return forces applied to the driven components of the mechanism may be controlled by lesser forces applied to the driving components of the mechanism.

Another specific object is to provide a ratchet drive mechanism in which the driving forces are transmitted to the driven components through a mechanism which becomes drivingly disengaged from the driven components upon the application of either an overriding or overpowering return torque to the driven components, and in which the return torque is transmitted to the driving components of the drive mechanism through another mechanism which becomes drivingly disengaged from the driven components when the driving forces are not being overpowered or overridden by return forces.

Another object is to provide a simple and effective ratchet drive mechanism for automatically effecting driving connection between a driving component and a driven component upon the application of a driving torque and for automatically disconnecting said components through the driving connection when the driven components either override the driving forces applied through such connec tion, or are reversed by a greater return torque than driving torque.

The novel features which are believed to be characteristic of this inveniton are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and method of operation, together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawing, in which:

FIG. 1 is a side elevational view of a drive mechanism embodying the invention.

FIG. 2 is a sectional view along the line 2-2 of FIG. 1.

FIG. 3 is an exploded perspective view of the mechanism shown in FIG. 1, certain parts being broken away or removed for clarification purposes.

With particular reference to FIG. 1, the apparatus shown therein includes a pair of parallel shafts, 1 and 2, a pair of different ratioed gears, or gear trains 3 and 4, which are mounted in axially spaced relationship on the shafts, and a pair of ratchet mechanisms 5 and 6 which are respectively associated with and disposed between gears 3 and 4. Gear or gear train 3 includes a pinion gear wheel 7 which is mounted and keyed on shaft 1 and a meshing spur wheel 8 which is freely rotatably mounted on shaft 2. Gear or gear train 4 is constituted by meshing spur wheels 9 and 10' which are respectively mounted on shafts 1 and 2. Drive shaft 1 is adapted to be connected to any suitable source of driving power and is suitably supported in bearings, such as by being journalled at one end in bearing 11 carried by upstanding end member 12. Shaft 2 is connected to any suitable load and is similarly suitably supported by being journalled at ice one end in bearing 13 carried by end member 12. End member 12 is supported on base plate 14.

Spindle support member 36 is fixed to shaft 2, and it is arranged to be bodily rotated about the axis of shaft 2. The gear wheels 8 and 10 are selectively connected to rotate with member 36 and, thus, with shaft 2, the connection of each being completed through ratchet mecha nism 5, in the case of wheel 8, and ratchet mechanism 6 in the case of wheel 10. The ratchet mechanisms are so arranged that the condition of one affects the condition of the other, as will become apparent from the description hereinafter set forth.

Ratchet mechanism 5 includes ratchets 15 and 16 which are respectively constituted by pawl 17 and ratchet wheel 18, and pawl 19' and ratchet wheel 20. The ratchet wheels 18 and 20 are separated by a radially extending washerlike collar 21 and wheel 18 is mounted adjacent hub 22 of spur wheel 8. As will be further explained subse quently, spur wheel 8, collar 21 and ratchet wheels 18 and 20 are rigidly interconnected and freely rotatable on shaft 2. Bearing sleeve 23 is fixed on shaft 2 adjacent the outer face of spur wheel 8 to restrain the spur wheel from axial movement in one direction. It will be understood that sleeve 23 is not affixed to wheel 8 but serves as a positioning bearing in contact with the side face of wheel 8. Pawls 17 and 19 are pivotally mounted at their outer ends on spindle 24 and extend inwardly thereof to engaging positions with respect to ratchet wheels 18 and 20 on opposite sides of shaft 2. The pawls are urged into engagement by generally transversely extending tension spring 25, the opposite ends of which are respectively connected to the respective pawls 17 and 19 adjacent their free ends. The axial component of tensive force exerted by spring maintains the free ends of pawls 17 and 19 adjacent collar 21 and the collar serves to maintain the free ends adjacent their respective ratchet wheels.

Ratchet mechanism 6 includes ratchets 26 and 27 which are associated with gear 4. Ratchet 26 is constituted by pawl 28 and ratchet wheel 29 whereas ratchet 27 comprises pawl 30 and ratchet wheel 31. The ratchet wheels 29 and 31 are separated by another washer like collar 32 and are rotatably connected to the hub 33 of spur wheel 10 and like spur wheel 10 are freely rotatably mounted on the shaft 2. Bearing sleeve 34 is fixed on shaft 2 adjacent the outer face of spur wheel 10 so as to restrain the wheel from axial movement in the direction of member 12, while permitting rotation of wheel 10 with respect to sleeve 34. Pawls 28 and 30 are pivotally mounted at their outer ends on spindle 24 and extend inwardly thereof to respective engaging positions with respect to ratchet wheels 29 and 31 on opposite sides of shafts 2. Tension spring 35 attaches at its opposite ends to the respective pawls 28 and 30 adjacent the free ends of the pawls.

Spindle 24 is mounted on radially extending support member 36. Support member 36 is disposed midway between the gears 3 and 4 and has a boss end 37 which is fixedly joined to shaft 2 so that the support member 36 as well as the pawls mounted thereon are rotatable therewith. The spindle 24 extends axially from the outer end 38 of the member 36 on either side thereof, and as previously indicated serves as a means upon which the pawls are pivotally mounted.

Sleeves 39 and 40 are mounted on shaft 2 respectively between the boss 37 and ratchet wheel 20, and the boss 37 and ratchet wheel 29, and extend radially outward from the ratchet wheels. The sleeves 39 and 40 function and serve as a means for restraining the inward axial movements of spur wheels 8 and 10.

Also shown in FIG. 1 is a guide bar 41 which is mounted on spindle 24 by means of end links 42 and 43. The links are pivotally attached to the opposite ends of spindle 24 and rigidly secured at the ends of the guide bar so that the bar 41 may swing with respect to spindle 24. Guide bar 41 serves as a means for selectively disengaging ratchets and 26 simultaneously in response to a driving connection by either ratchet 16 or 27, and for disengaging ratchets 16 and .27 simultaneously in response to a driving connection by either ratchet 15 or 26.

The function of guide bar 41 is best illustrated by reference to FIG. 2 and its action relative to ratchets 26 and 27. As shown therein the teeth 46 of ratchet wheel 31 extend in a counterclockwise direction whereas the teeth 47 of ratchet wheel 29' extend in a clockwise direction. Accordingly, ratchets 26 and 27' are adapted to selectively drivingly connect in response to rotary forces. exerted in opposite directions on shaft 2. The teeth 48 and 49 of ratchet wheels 18 and 20 respectively are simi larly oppositely directed for driving engagement.

As shown in FIG. 2, bar 41 is suspended from the spindle 24 in a position such that it extends between the pivotally mounted pawls 28 and 30. Pawl 28 extends from its pivotal mounting on spindle 24 inwardly therefrom and to one side of bar 41 whereas pawl 30 extends from its pivotal mounting inwardly therefrom and to the other side of bar 41. Spring tends to urge the engaging tips 44 and of pawls 30 and 28 respectively inwardly toward shaft 2 in a scissor-like manner, and the bar 41 is so disposed between the pawls 30 and 28 as to. engage the pawls and thereby maintain the tips 44 and 45 of the pawls in a predetermined minimum spaced relationship. The minimum spacing is such that when one of the pawls 30 or 28 is fully engaged by the teeth of its respective ratchet wheel that the other pawl is fully disengaged from its ratchet wheel, and is furthermore such that upon disengagement of one pawl from its ratchet wheel, the other pawl is forced into an engagingiposition with respect to its ratchet. Thus, the engaging tip 44 0f pawl 30 is shown fully engaged between the teeth 46 of ratchet wheel 31 whereas pawl 28 is so disposed because of the position of bar 41 that the engaging tip 45 of pawl 28 is fully disengaged. Rotation of ratchet wheels.29-and'31 in the direction of arrow 50 will cause thetip 44 ofpawl 30 to be displaced by tooth 52 of wheel 31 outwardly from ratchet wheel 31 in the direction of arrow 51, and as this displacement takes place spring '35 will urge pawl 28 and accordingly the bar 41 in the same direction as arrows 51. Thereafter. as the tip 45 of pawl 28 engages and becomes seated between the teeth 47 of ratchet wheel 29 the bar 41 becomes further displaced and accordingly the tip 44 of pawl 30 becomes fully disengaged. The displacement of the bar 41 in accord with the urgings of spring 35 on pawl 28 also displaces pawl 19' into a fully disengaged position and accordingly it will be seen that the bar 41 senses a driving connection and disengages the ratchets which tend to drivingly connect in the direction opposite thereto.

Also shown in FIG. 3 is key 53 which rotatably connects shaft 1 and spur wheel 9, and pin 54 which rigidly secures spur wheel 10, ratchet wheels 29 and 31, and collar 32 so that they are mutually freely rotatable on shaft 2.

With reference to FIG. 3, pin 55 is provided for rigidly connecting spur wheel 8, ratchet wheels 18 and 20 and collar 21 for free rotation of shaft 2. Pin 55 is not, however, engaged in collar 23 and does not connect collar" 23 or member 36 to wheels 8, 18 and 20. A screwdriverv The operation of the drive mechanism will be best understood by the following whereas it will be evident that as between shafts the driving forces are transmitted upon one shaft to the other shaft through the gear offering the least mechanical advantage. Accordingly, when the driving force applied to shaft 1 is controlling, the drive connection with shaft 2 is established through the ratchet mechanism associated with. gear 4 since this offers the least mechanical advantage in the direction of drive. On the other hand, when an overpowering force is exerted on shaft 2 whichovercomesthe: driving force exerted on shaft 1, or when an overriding force is exerted on shaft 2, the overpowering or overriding force as the case may be is transmitted to shaft 1 through the mechanism associted with gear 3 since this mechanism oifers the lesser mechanical advantage for such return driving forces.

It will be first assumed for purposes of illustrating the operation of the drive mechanism that the drive shaft 1 is beingdriven in the direction of arrow 59. Under these conditions it will be apparent that the driving torque applied to the drive shaft 1 will cause both pinion 7 and spur wheel 9 to rotate. in the same direction, as shown by arrows 60 and 61 respectively. The rotation of the pinion 7 and spur wheel 9 will in turn cause the resp'ec tive spur wheels 8 and 10 to rotate in the directions in-' dicated by arrows 62 and 63. Because of the difference in gear ratios between gear 3 and gear 4, the freely rotatable gear wheel 10, under these driving conditions, will cause the. ratchet wheels 29 and 31 to rotate at a greater speed than the gear wheel 8 will cause the ratchet wheels 18 and20 to rotate. Accordingly, the teeth 46' of ratchet wheel 31 will engage the tip 44 of pawl 30 and thereby transmit the rotary force to the shaft 2 through the in= tervening support member 36, and the support member 36 and elements mounted thereon will rotate in the direc tion of arrow 65 shown in FIG. 2. As the ratchet wheel 31 and pawl 30 engage, bar 41 is displaced toward pawls 17 and 28 in the direction of arrow '64 as viewed in FIG 2. This displacement of the sensing bar 41 causes the pawls 17 and 28 to assume a disengaged position with re spect to their respective ratchet wheels 18 and 27 respectively. Pawl 19, on the other hand, is urged into contact with ratchet wheel 20 by spring 25 as a consequence of the displacement of sensing bar 41 but, nevertheless, fails to drivingly connect because the speed at which the shaft 2 and the supported pawl members rotate in the directionof arrow 65 is in excess of the rotational speed imparted to ratchet wheel 20 through gear 3. Accordingly, pawl 19 merely ratchets along the surface of the teeth 49 of ratchet wheel 20.

In the event that an overriding force is exerted on'shaft 2, that is, a force applied externally to shaft 2 which drives the shaft 2 and the supported pawls in a direction to cause them to revolve at a greater speed in the direction of arrow 65 than that caused by the driving force exerted through the mechanism associated with gear 4, then, under these circumstances, pawl 30 is forced out of engagement with ratchet wheel 31 thereby permitting bar 41 to swing in the direction of arrow 66 in response to the urgings of spring 35 on pawl 23. This change of position by bar 41 displaces pawl 19 in the same direction and pawl 17, associated with gear 3, is drawn into engagement with the teeth 48 of ratchet wheel 18 in accord with the urgings of spring 25, and the driving connection between the shafts is assumed by ratchet 15. Although pawl 28 is drawn into contact with ratchet wheel 29 by the overriding force, no driving connection is made by ratchet 26 for the reason that the driving connection by ratchet 15 causes the spur wheel 8 to rotate the pinion 7 in the direction of arrow 59 at a speed in excess of that caused by the driving force on shaft 1. In turn, this causes spur wheel 10 to rotate in the direction of arrow 63 at a speed in excess of the rotary motion of shaft 2, and accordingly pawl 28 merely ratchets along the outer surface of the teeth 47 of ratchet wheel 29.

To illustrate the operation of the mechanism when an overpowering force is applied to the driven shaft 2, it will be assumed that shaft 1 is being driven in the direction of arrow 59 in accord with the prior description, and accordingly that the driving connection between the shafts 1 and 2 exists through ratchet 27. It will be apparent that under such circumstances that the overpowering torque exerted on the driven components of the apparatus will be exerted in the direction of arrow 67. Such an overpowering force or torque would be an external force resisting rotation of shaft 2, that is, tending to rotate shaft 2 in direction 67, and opposing the driving of shaft 2 by ratchet 27. If viewed in increments of motion, the overpowering force will ultimately halt the rotation of shaft 2 and accordingly the mechanism suspended on support 22. Thereafter shaft 2 and the pawl supporting mechanism will tend to rotate in the direction of the overpowering force as illustrated by arrow 67 in FIG. 3 and by arrow 68 in FIG. 2. As this happens, pawl 19, which previously has been ratcheting along the surface of ratchet wheel 20 will engage the teeth of ratchet wheel 20 and thereby cause the overpowering torque to be transmitted to shaft 1 through gear 3. It will be seen that engagement of pawl 19, through bar 41, will swing pawl 28 out of engagement with the teeth of ratchet wheel 29. This transmission of the overpowering force to the gear 3 will cause spur wheel to rotate in the direction of arrow 69 and at a greater rotational speed than that of the shaft 2 and the pawl supporting mechanism in the same direction. Accordingly pawl 30 will become disengaged from the teeth of ratchet wheel 31 and thereafter ratchet along the surface of the teeth of wheel 31.

The function of the drive mechanism is substantially the same regardless of which direction the driving force is applied to drive shaft 1. If the driving force is applied in the direction of arrow 70 the driving connection with shaft 2 will be made through ratchet 26 via gear 4. As this connection is made bar 30 is displaced in the direction of arrow 66 and ratchets 16 and 27 are disengaged while the pawl 17 of ratchet ratchets along the surfaces of wheel 18. An overpowering force or an overriding force exerted on driven shaft 2 under these circumstances will cause the mechanism to operate in substantially the same manner as previously explained, except that the driving connections under such circumstances will be made through ratchets 16 and 15 respectively.

From the foregoing it will be evident that whenever a driving force is exerted upon the drive shaft 1, the driven shaft 2 is drivingly connected thereto through the ratchet mechanism 6 associated with gear 4, whereas when there I is an overpowering force or an overriding force exerted on the driven shaft 2 the driving connection is then made through the ratchet mechanism 5 and gear 3.

While only a certain preferred embodiment of this invention has been shown and described by way of illustration, many modifications will occur to those skilled in the art and it is, therefore desired that it be understood that it is intended in the appended claims to cover all such modifications as fall within the true spirit and scope of this invention.

What is claimed as new and what it is desired to secure by Letters Patent of the United States is:

1. In combination, a rotatable shaft, two gear wheels freely rotatable on said shaft, two ratchet wheels having respectively oppositely oriented teeth fixed to each said gear wheel, a pawl for each said ratchet wheel, each of said pawls being pivotally mounted on a common pivotal mount spaced laterally from said shaft, means fixed to said shaft supporting said mount in fixed position with respect to said shaft and rotatable therewith, rod means extending between said pawls operative to disengage one pawl of one pair from its respective ratchet wheel in response to engagement of one pawl of the other said pair and to disengage the other pawl of said one pair in response to engagement of said other pawl of said other 6.. pair with its said ratchet wheel, and force transmitting gear means engaged with said gear wheels.

-2. In a drive mechanism, a drive shaft and a driven shaft, a first and a second gear train each drivingly connected to one of said shafts and each including a respective gear wheel freely rotatably mounted on said other shaft, a first pair of ratchet wheels having respective teeth oriented in the same direction respectively drivingly connected to said gear wheels of said first and second gear trains, a second pair of ratchet Wheels having respective teeth oriented in the opposite direction to those of said first pair of ratchet wheels and respectively drivingly connected to said gear wheels of said first and second gear trains, a first pair of pawls pivotally attached to and rotatably carried by said other shaft respectively engageable with the ratchet wheels of said first pair of ratchet wheels, a second pair of pawl-s pivotally attached to and rotatably carried by said other shaft respectively engageable with the ratchet wheels of said second pair of ratchet wheels, and means interconnecting said pairs of pawls for disengaging the pawls of said first pair of pawls from their respective ratchet wheels in response to driving engagement by one of said pawls of said second pair of pawls with its respective ratchet Wheel and for disengaging the pawls of said second pair of pawls from their respective ratchet wheels in response to driving engagement by one of said pawls of said first pair of pawls with its respective ratchet wheel.

3. In a drive mechanism, a drive shaft and a driven shaft, 2. first gear train and a second gear train respectively drivingly connected to one of said shafts and each said train including a respective gear Wheel freely rotata'bly mounted on the other of said shafts, a firs-t pair of ratchet wheels having respective teeth oriented in the same direction freely rotatably mounted on said other shaft and respectively drivingly connected to said first and second gear trains, a second pair of ratchet wheel-s having re spective teeth oriented in the opposite direction to said first pair of ratchet wheels freely rotatably mount-ed on said other shaft and drivingly connected to said first and second gear trains respectively, a support member freely rotatably mounted on said other shaft, 2. first pair of pawls pivotally attached to and carried by said support member, the pawls of said first pair being respectively engageable with respective ratchet wheels of said first pair of ratchet wheels, a second pair of pawls pivotally attached to and carried by said support member, the pawls of said second pair being respectively engageable with respective ratchet wheels of said second pair of ratchet Wheels, bar means carried by and movable with respect to said support member and engageable with respective said pawls for disengaging said first pair of pawls from their respective ratchet wheels of said first pair of ratchet wheels in response to driving engagement by one of said pawls of said second pair of pawls with its respective ratchet wheel of said second pair of ratchet wheels and for disengaging said second pair of pawls from their respective ratchet wheels of said second pair of ratchet wheels in response to driving engagement by one of said pawls of said first pair of pawls with its respective ratchet wheel of said first pair of ratchet wheels.

4. In a drive mechanism, a pair of shafts, a pair of gear trains drivingly connected to one of said shafts, each said train including a respective gear wheel and freely rotatably mounted on the other of said shafts, a support member fixedly carried by said other shaft, a first pair of ratchet wheels freely rotatably mounted on said other shaft having respective teeth oriented in the same direction and respectively drivingly connected to one and the other of said pair of gear trains, a first pair of pawls through first pair of ratchet wheels, a second pair of ratchet Wheels freely rotatably mounted on said other of said shafts having respective teeth oriented in the opposite direction to said first pair of ratchet wheels, a second pair of pawls pivotally mounted on said support respectively engageable with respective ratchet wheels of said second pair of ratchetwheels, a bar pivotal-1y connected to said support member and disposed engagingly between said first and second pairs of pawls, said bar being arranged and adapted to selectively disengage said second pair of pawls from their respective ratchet wheels upon driving engagement between one of said pawls of said first pair of paWls and its respective ratchet wheel and to disengage said first pair of pawls from their respective ratchet wheels upon driving engagement between one of said pawls of said second pair of pawls and its respective ratchet wheel.

5. In a drive mechanism, a rotatable shaft, a pair of gear wheels freely rotatably mounted on said shaft, a support member mounted on and rotatable with said shaft, a first pair of ratchet wheels freely rotatably mounted on said shaft and drivingly connected to one of said gear Wheels, said ratchet wheels having, respectively oppositely oriented teeth, a first pair of pawls pivotally mounted on said member adapted and arranged to engage respective said ratchet wheels on opposite sides of said shaft, first spring means urging said pawls into engagement with their respective said ratchet wheels, a second pair of ratchet Wheels freely rotatably mounted on said shaft and drivingly connected to the other of said 8. gear Wheels, said ratchet Wheels of said second pair having respectively oppositely oriente'da" second pair of pawls pivotally mounted on said-=member adapted and arranged to engage respective saidiratchet Wheels of said second pair of ratchet wheels onopposite sides of said shaft, second spring means urging said second pair of pawls into engagement with their respective said ratchet wheels of said second pair of ratchet wheels, bar means-extending between and engageable with said pawls and pivotally attached to said support member outwardly of said shaft, said bar means being arranged and adapted to urge the respective pawl of each said pair which is engageable with its said ratchet wheel on one side of said shaft out of such engagement in response to engagement by one of said pawls on the other side of said shaft with its respective ratchet wheel.

References Cited in the file of this patent UNITED STATES PATENTS 2,246,996 Kreis June M, 1941 2,772,576 Ross Dec. 4, 1956 FOREIGN PATENTS 165,411 Great Britain Nov. 24, 1921 

